Text Appearing Before Image:Fig. 59. The axis, or the sec-ond vertebra, viewed from theside : (1) the process on whichthe atlas turns seen also at 1,(Figs. 58, and 60) ; (2) the placeon which the atlas rests. 170 THE ESSENTIALS OF HEALTH. on the sides, and the diaphragm below. The spaces be-tween the ribs are filled in with muscular tissue, so thatsurrounding the thoracic cavity there is a complete wall,formed partly of bone and partly of muscle. All that partText Appearing After Image:Fig. 60. The atlas and axis in position, front view : (1) the tooth-like process of the axis, showing above the atlas; (2) the axis ; (3) theatlas. of Fig. 43 which is above the diaphragm, 6, representsthe thorax, or chest, with its contents in place. In thiscavity are the lungs, heart, and large blood vessels. The Upper Extremities. There are five large bonesand several small ones that belong to the upper ex-tremity. The clavicle, or collar bone, extends from thefront of the shoulder to the top of the sternum ; it keepsthe shoulder joint outward and backward. The scapula,or shoulder blade, forms the back part of the shoulder,and is between the shoulder joint and the spine ; at itsupper and outer part is a cavity, or socket, for the re-ception of the head of the humerus. The humerus, orarm bone, extends from the shoulder to the elbow. Itshead is round, forming a ball for the ball-and-socketjoint at the shoulder; the lower end is flattened andgrooved, to make the hinge joint of the elb

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